Workbooks.Open returns different file than Filename - vba

Question

I am having the strangest problem. I was writing the below code on my laptop the other day and it worked fine. Now, I am testing it on my desktop and it's stopped working.
First, here's my code
Dim oApp As Application
Dim oWb As Workbook
Set oApp = New Application
oApp.Visible = True
Set oWb = oApp.Workbooks.Open(Filename:="C:\myFile.xlsx", ReadOnly:=True)
debug.print oWb.name
'returns "SOLVER.XLAM"
' "SOLVER.XLAM" is not "myFile.xlsx'
debug.print oApp.Workbooks.Count
'returns 1
debug.print oApp.Workbooks(1).name
'returns "myFile.xlsx"
Now, I know that solver is an add in, and it gets loaded in the new application upon creating it... but how does it perform this switcheroo? I can still get to the correct file, but I don't want to risk it on the coincidence that there is only 1 file in my Application object (or that the first file is the one I loaded)
Additional Info
I am calling executing this macro from within an excel instance and I wish to open a separate excel instance and then open particular workbook ("C:\myFile.xlsx") inside that other instance.
The key problem I'm having is that when I open the other instance and then add the workbook and set it to my oWb variable... somehow, when I later call that oWb variable it refers to something different from what I had set it to.
'This is how it makes me feel:
Dim x As Integer
x = 5
Debug.Print x
' 12

Answer 1

I think if you just refine your code a bit to ensure you are doing exactly what you want, you will be fine. Since it's unclear whether you are calling the code from within Excel or another MS Office Application, I placed to subs below.
Run this if running it in Excel:
Option Explicit
Sub insideXL()
Dim oWb As Workbook
Set oWb = Workbooks.Open("C:\myFile.xlsx", ReadOnly:=True)
Debug.Print oWb.Name
Debug.Print Workbooks.Count
Debug.Print Workbooks(1).Name
oWb.Close false
Set oWb = Nothing
End Sub
Run this if running in another program. I use early binding, but you could use late binding as well, if you wish:
Sub outsideXL()
'make sure Microsoft Excel X.X Object Library is checked in Tools > References
Dim oApp As Excel.Application
Set oApp = New Excel.Application
Dim oWb As Excel.Workbook
Set oWb = oApp.Workbooks.Open("C:\myFile.xlsx", ReadOnly:=True)
oApp.Visible = True
Debug.Print oWb.Name
Debug.Print Workbooks.Count
Debug.Print Workbooks(1).Name
oWb.Close = True
Set oWb = Nothing
Set oApp = Nothing
End Sub

Answer 2

I found that this (which worked in 2007):
wb = excel.Workbooks.Open(filename, False, True)
needs to be written
excel.Workbooks.Open(filename, False, True)
wb = excel.ActiveWorkbook
for 2010